We keep hearing that airborne drones may some day deliver online orders to our doors, but there's another technology being tested in congested cities - using robots on the ground.

At this time, two Peninsula cities now have them and on Tuesday San Carlos got to test out the delivery robot.

Young twins Logan and Maxwell Shen were captivated the moment they saw a tiny robot barely bigger than themselves. It's going to be a common sight in San Carlos, as this new robot will be delivering cupcakes or other food ordered on the Postmates app.

The pilot program requires a human handler to be nearby to answer questions and to intervene for safety reasons.

On Tuesday, the robot took cupcakes locked inside its storage compartment and made its way down sidewalks, paused at driveways, and even waited for traffic before crossing the street.

The robot is made in Estonia by Starship Technologies, which has deployed them in 60 cities in 15 countries. Its primary purpose is to make online order delivery eco-friendly. "As more and more people order more and more things online, it simply means there are going to be more bikes, more cars, more vans on the road. We're looking to reduce that and assist that problem using our zero-emissions delivery robots," Starship Technologies spokesperson Henry Harris-Burland said.

Some San Carlos residents who spotted the robot think it'll help in other ways. "You can't buy a parking space at night on Laurel Street, so this will be a great thing for delivery food to people at home," San Carlos resident Jim McGraw said.

The robot travels at about four miles an hour.

Redwood City was first in the area to test the robots, and its success has the city thinking of new ways to use them. "We do look to expand it to possibly other things, maybe working with our library or some of our retail businesses as well beyond the restaurant delivery," Redwood City economic development director Catherine Ralston said.